1. Field of the Invention
The invention relates to methods and compositions for reducing fluid loss in viscoelastic treatment fluids that are essentially free of polymers.
2. Description of the Related Art
Treatment fluids are used in a variety of subterranean treatments. Such treatments include drilling operations, stimulation treatments, sand control treatments, and the like. Treatment fluids are generally viscosified to enable the treatment fluids to perform such tasks as transporting solids in drilling operations and transporting particulates, such as proppant, in fracturing operations.
Polysaccharide polymers have been used in the past to form the aqueous gels that were used as treatment fluids. The polysaccharide polymers were typically crosslinked in order for the treatment fluid to have the necessary viscosity to perform its intended task, such as transporting proppant in fracturing jobs. Once the treatment process was complete, the treatment fluid often required a significant amount of time and additional well treatment additives to remove the polymer gel, such as bactericides, antifoam agents, surfactants to aid dispersion, pH control agents, chemical breakers, enzymatic breakers, iron control agents, fluid stabilizers, antioxidants, salts, and the like. These additives must be formulated correctly, transported to the jobsite, and then pumped and metered accurately during the execution of the treatment. Complete removal of the polymer was difficult, often times resulting in residual polymer being left in the formation that clogged the pores of the formation, which prevented hydrocarbons from flowing through and from the formation.
The use of non-polymeric treatment fluids has increased in recent times because of the desirable properties of such non-polymeric treatment fluids. Such properties include the ability to transport proppant at lower viscosities than the polymer-based treatment fluids, the reduction of friction between the treatment fluid and the surfaces contacted therewith, and the quick reduction in viscosity upon contact with hydrocarbons. The non-polymeric treatment fluids contain viscoelastic surfactant gels that do not contain polymers. Because the treatment fluids do not contain polymers, they do not have a polymeric backbone structure to help obstruct the fluid from passing through the pore throats of the formation. While the benefits of using the viscoelastic treatment fluids are apparent, the lack of polymeric structure in these viscoelastic treatment fluids unfortunately can result in a high amount of fluid loss in treatment operations.
A need exists for methods and compositions that can be used in treatment operations that would benefit from the use of viscoelastic treatment fluids, but without the substantial amount of fluid loss that is typically encountered in such systems. It would be advantageous if such methods and compositions did not adversely affect the rheology of the viscoelastic treatment fluids.